This invention concerns improvements in or relating to glass compositions, fiber made therefrom and cementitious materials including such fiber as reinforcement.
Glass compositions, containing beryllia, magnesia, strontium oxide, titania, cadmium oxide or zirconia have been known for many years (see, for example, U.K. Patent Specification Nos. 595,498 and 791,374 and U.S. Pat. No. 2,640,784). From these, refractory glass fiber and other articles may be made.
More recently, U.S. Pat. No. 2,877,124 discloses compositions which are chemically durable, have a low liquidus temperature and slow devitrification and are capable of being formed into fibers by rotary spinning and attenuation of the strands so obtained. These compositions comprise, in weight percent; SiO.sub.2 50 to 65 Al.sub.2 O.sub.3 0 to 8 CaO 3 to 4 MgO 0 to 10 Na.sub.2 O,K.sub.2 O,Li.sub.2 O 10 to 20 B.sub.2 O.sub.3 5 to 15 TiO.sub.2 0 to 8 ZrO.sub.2 0 to 8 BaO 0 to 8 Fe.sub.2 O.sub.3 0 to 12 MnO 0 to 12 ZnO 0 to 2
And preferably are essentially free from at least a majority of the six last-named components.
U.S. Pat. No. 3,127,277 discloses glasses of high modulus of elasticity, of composition, in weight percent:
SiO.sub.2 45 - 60 CaO 9 - 19 MgO 6 - 10 BeO 7 - 12 ZrO.sub.2 1 - 3 Li.sub.2 O up to 4 TiO.sub.2 2 - 10 CeO.sub.2 up to 4
Optionally including other ingredients such as Fe.sub.2 O.sub.3 and Al.sub.2 O.sub.3.
U.S. Pat. No. 3,817,764 discloses glass compositions, in weight percent:
SiO.sub.2 49 - 57 Al.sub.2 O.sub.3 3 - 5 B.sub.2 O.sub.3 6 - 12 Na.sub.2 O 18 - 20 CaO 0 - 2 TiO.sub.2 9 - 12 ZrO.sub.2 0 - 7 Fe.sub.2 O.sub.3 0 - 0.5 LiO.sub.2 0 - 1
and states that glass fibers which are especially water durable, and can be made from these compositions by rotary or centrifugal spinning.
Finally, U.S. Pat. No. 3,861,925 discloses alkali resistant fiberizable glass compositions which are zirconia free and consist essentially of, in weight percent.
______________________________________ SiO.sub.2 55 - 65 TiO.sub.2,La.sub.2 O.sub.2 or CeO.sub.2, 12 - 25 CaO 4 - 6 Na.sub.2 O. 12 - 18 K.sub.2 O 0 - 3 ______________________________________
Despite such disclosures, however, there is still a need for glasses having improved chemical durability -- in particular improved resistance to alkali attack, for example for use in reinforcing cementitious articles.